Add forward_variables_from() and target() to GN

tools/gn/function_forward_variables_from_unittest.cc

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "testing/gtest/include/gtest/gtest.h"
+#include "tools/gn/scheduler.h"
+#include "tools/gn/test_with_scope.h"
+
+TEST(FunctionForwardVariablesFrom, List) {
+  Scheduler scheduler;
+  TestWithScope setup;
+
+  // Defines a template and copy the two x and y, and z values out.
+  TestParseInput input(
+    "template(\"a\") {\n"
+    "  forward_variables_from(invoker, [\"x\", \"y\", \"z\"])\n"
+    "  assert(!defined(z))\n"  // "z" should still be undefined.
+    "  print(\"$target_name, $x, $y\")\n"
+    "}\n"
+    "a(\"target\") {\n"
+    "  x = 1\n"
+    "  y = 2\n"
+    "}\n");
+
+  ASSERT_FALSE(input.has_error());
+
+  Err err;
+  input.parsed()->Execute(setup.scope(), &err);
+  ASSERT_FALSE(err.has_error()) << err.message();
+
+  EXPECT_EQ("target, 1, 2\n", setup.print_output());
+  setup.print_output().clear();
+}
+
+TEST(FunctionForwardVariablesFrom, ErrorCases) {
+  Scheduler scheduler;
+  TestWithScope setup;
+
+  // Type check the source scope.
+  TestParseInput invalid_source(
+    "template(\"a\") {\n"
+    "  forward_variables_from(42, [\"x\"])\n"
+    "  print(\"$target_name\")\n"  // Prevent unused var error.
+    "}\n"
+    "a(\"target\") {\n"
+    "}\n");
+  ASSERT_FALSE(invalid_source.has_error());
+  Err err;
+  invalid_source.parsed()->Execute(setup.scope(), &err);
+  EXPECT_TRUE(err.has_error());
+  EXPECT_EQ("Expected an identifier for the scope.", err.message());
+
+  // Type check the list. We need to use a new template name each time since
+  // all of these invocations are executing in sequence in the same scope.
+  TestParseInput invalid_list(
+    "template(\"b\") {\n"
+    "  forward_variables_from(invoker, 42)\n"
+    "  print(\"$target_name\")\n"
+    "}\n"
+    "b(\"target\") {\n"
+    "}\n");
+  ASSERT_FALSE(invalid_list.has_error());
+  err = Err();
+  invalid_list.parsed()->Execute(setup.scope(), &err);
+  EXPECT_TRUE(err.has_error());
+  EXPECT_EQ("Not a valid list of variables to copy.", err.message());
+
+  // Programmatic values should error.
+  TestParseInput prog(
+    "template(\"c\") {\n"
+    "  forward_variables_from(invoker, [\"root_out_dir\"])\n"
+    "  print(\"$target_name\")\n"
+    "}\n"
+    "c(\"target\") {\n"
+    "}\n");
+  ASSERT_FALSE(prog.has_error());
+  err = Err();
+  prog.parsed()->Execute(setup.scope(), &err);
+  EXPECT_TRUE(err.has_error());
+  EXPECT_EQ("This value can't be forwarded.", err.message());
+}
+
+TEST(FunctionForwardVariablesFrom, Star) {
+  Scheduler scheduler;
+  TestWithScope setup;
+
+  // Defines a template and copy the two x and y values out. The "*" behavior
+  // should clobber existing variables with the same name.
+  TestParseInput input(
+    "template(\"a\") {\n"
+    "  x = 1000000\n"  // Should be clobbered.
+    "  forward_variables_from(invoker, \"*\")\n"
+    "  print(\"$target_name, $x, $y\")\n"
+    "}\n"
+    "a(\"target\") {\n"
+    "  x = 1\n"
+    "  y = 2\n"
+    "}\n");
+
+  ASSERT_FALSE(input.has_error());
+
+  Err err;
+  input.parsed()->Execute(setup.scope(), &err);
+  ASSERT_FALSE(err.has_error()) << err.message();
+
+  EXPECT_EQ("target, 1, 2\n", setup.print_output());
+  setup.print_output().clear();
+}